linux-kernel - Re: [PATCH, RFC] reimplement flush

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20061218170028.eaa1faf0.akpm@osdl.org>
Date:	Mon, 18 Dec 2006 17:00:28 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	David Howells <dhowells@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...l.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC] reimplement flush_workqueue()

On Tue, 19 Dec 2006 03:43:19 +0300
Oleg Nesterov <oleg@...sign.ru> wrote:

> On 12/18, Andrew Morton wrote:
> >
> > On Mon, 18 Dec 2006 01:34:16 +0300
> > Oleg Nesterov <oleg@...sign.ru> wrote:
> > 
> > > NOTE: I removed 'int cpu' parameter, flush_workqueue() locks/unlocks
> > > workqueue_mutex unconditionally. It may be restored, but I think it
> > > doesn't make much sense, we take the mutex for the very short time,
> > > and the code becomes simpler.
> > > 
> > 
> > Taking workqueue_mutex() unconditionally in flush_workqueue() means
> > that we'll deadlock if a single-threaded workqueue callback handler calls
> > flush_workqueue().
> 
> Well. But flush_workqueue() drops workqueue_mutex before going to sleep ?
> 
> 	flush_workqueue(single_threaded_wq);
> 		...
> 		mutex_lock(&workqueue_mutex);
> 		...
> 		mutex_unlock(&workqueue_mutex);
> 		wait_for_completition();
> 							handler runs,
> 							calls flush_workqueue(),
> 							workqueue_mutex is free

Oh.  OK.  In that case we can switch to preempt_disable() for the
cpu-hotplug holdoff.  Sometime.

> > It's an idiotic thing to do, but I think I spotted a site last week which
> > does this.  scsi?  Not sure..
> 
> Ok, it is time to sleep. I'll look tomorrov and re-send if flush_cpu_workqueue()
> really needs "bool workqueue_mutex_is_locked" parameter.

Hopefully not.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/